Until now, religions have been remarkably silent on nanotechnology, Toumey points out. Nothing compared to the harsh bioethical controversies about in vitro fertilisation in the Catholic world, for example. "Nanotechnology is a heterogeneous body of sciences and technologies: few faith communities have enough universities or journals to examine such a complicated issue," says Toumey. "Their attention may be attracted if some dramatic event happens: either positive, something like a cure for a cancer, or negative, like an environmental disaster." The scarcity of official documents makes it difficult to guess religious views, but it is an opportunity for scientists to get prepared in advance.